Circular-type antenna with symmet-rically movable arms providing capacitive and inductive variation for tuning



Mamh 1955 J. B. CARAWAY CIRCULAR-TYPE ANTENNA WITH SYMMETRICALLY MOVABLEARMS PROVIDING CAPACITIVE'AND INDUCTIVE VARIATION FOR TUNING Filed June6, 1962 INVENT OR Jay/v5. (ZR/1W4) BY who, gmub .x mm

ATTORNEYS CIRCULAR-TYPE ANTENNA WITH SYMMET- RICALLY MOVABLE ARMSPROVIDING CA- PACITIVE AND INDUCTIVE VARIATION FOR TUNING John B.Caraway, Newburgh, Ind., assignor to Electronics Research, Inc.,Evansville, Ind., a corporation of Indiana Filed June 6, 1962, Ser. No.200,580 1 Claim. (Cl. 343--744) This invention relates to antennae forradio apparatus and more particularly antennae for use in high frequencytransmissions systems. One example of the type of antenna involved isshown in Patent No. 2,467,961, issued to John B. Caraway, Jr., and H.Kees on April 19, 1949.

High frequency antenna systems are well known in the art, however, theseknown systems exhibit certain disadvantages. One of the disadvantages isthat of frequency limitation imposed upon the antenna systems by thenature of their construction.

Accordingly, it is an object of this invention to provide an improvedhigh frequency antenna system which obviates the above mentioneddisadvantage.

It is another object of this invention to provide an improved circulartype high frequency antenna which may be easily adjusted over arelatively broad range of frequencies.

It is still another object of this invention to provide an improvedcircular type antenna which can be tuned over a relatively wide range offrequencies by varying the inductance of the antenna.

It is still another object of this invention to provide a circular typeantenna which can be tuned over a relatively wide range of frequenciesby adjusting the inductance as well as the capacitance of the antenna.

It is still another object of this invention to provide an improvedcircular type antenna in which the inductance and input impedance can bevaried.

Briefly, in accordance with aspects of one illustrative embodiment ofthis invention, I provide a segmented circular type high frequencyantenna in which the ends of the segments of the circle are mounted on ablock in such a manner that the ends of the segments may be movedrelative to each other, thereby varying the diameter of the circle. Thisvariation causes the inductance of the antenna to be varied.

In accordance with other aspects of this invention, capacitor plates areconnected to the opposite ends of the segments from the mounting blockand the distance between these capacitor plates will be varied in thesame direction as the diameter of the circle. Thus, the capacitance ofthe antenna will be varied simultaneously with the inductance.

In accordance with still other aspects of this invention, I connect tothe feed line with a flexible strap a feed strap clamp on the circularantenna. Advantageously, the clamp is provided with an adjustablecoupling so that the clamp may be loosened and displaced relative to thesegment of the circle, thereby changing the effective input impedance ofthe antenna.

United States Patent These and various other objects and features of theinvention will'be more clearly understood by a reading of the detaileddescription in conjunction with the drawing in which:

FIG. 1 is a plan view of one illustrative embodiment of this invention;

FIG. 2 is a view in elevation of the embodiment of FIG. 1; and,

FIG. 3 is a side view of FIG. 2.

Referring now to the drawing, there is depicted a loop block 11 having aloop mounting plate 12 secured there- 3,176,299 Patented Mar. 30, 1965to by any convenient means such as by welding. A pair of circularsegments or semi-circular conductors 13 and 14 terminate at one end inrectangular blocks 15 which blocks are threaded to receive suitablebolts 16 which pass through the plate 12 to threadably engage the blocks15. I

The segment 13 includes a pair of spaced circular conductors Whilesegment 14 includes a pair of spaced circular conductors with T section17, shown in FIGS. 2 and 3, lying on its side with one end connected toblock 15 and the other ends connected to the spaced circular conductors.It is understood that the spacing between the conductors of a pair isarbitrary while spacing between the pairs of conductors determines theinductance of the antenna.

Advantageously, elongated slots 18 are provided in the loop mountingplate 12, such that the bolts 16 may be loosened and the semi-circularloops or segments 13 and 14 displaced relative to each other and thebolts 16 subsequently tightened. Variation of this relative displacementvaries the inductance of the antenna. On the opposite ends of theantenna segments 13 and 14 from the mounting block 11, a pair ofcapacitor plates 19 are mounted in substantially parallel relationship.The capacitance of this capacitor will be varied as the plates aredisplaced relative to each other. Thus, the capacitance of the antennawill be varied at the same time that the inductance is varied. The meansused to adjust the antenna to change the diameter of the pairs ofsemicircular segments can be any number of structures such as leadscrews, spacers, cams, slots in a backup plate as shown in the drawingor any means that would change the diameter and thereby increase ordecrease the inductance of the loop antenna.

A feed-through insulator or bushing 21 is secured to the loop block bysuitable means such as by bolt 22 and nuts 24, 26 and 28. An 0 ring 29is mounted between bushing 21 and block 11 to provide a moisture seal.Bolt 22 is connected to a suitable conductor 30 which passes through theinsulating bushing 32 in a direction substantially perpendicular to bolt22.

A clamping member 34 is clamped to circular segments 14 by suitablemeans such as a pair of nut and bolt assemblies 37. Advantageously, aflexible conducting strap 38 is connected to the bolt 22 between nuts 24and 26 and is connected to clamp 34 to supply high frequency energy tothe segment 14. Since these bolt assemblies 37 may be loosened and theclamp 34 moved relative to the segment 14, the point at which energy issupplied to the antenna and thus the input impedance is varied. It isunderstood, of course, that the loop mounting plate is grounded orconnected to the other side of the feed line to which conductor 30 isconnected to provide the necessary return path for the electricalenergy.

When it is desired to vary the frequency at which the antenna isadjusted, bolts 16 are loosened and the segments 13 and 14 are movedrelative to each other to change the distance between the segments whichdistance is indicated by the double-headed arrow 20. When the segmentshave been moved relative to each other, the bolts 16 are againtightened. This adjustment of the antenna varies the inductance bychanging the distance indicated by the double arrow 20 and also changesthe capacitance because it changes the distance between the capacitorplates 19 indicated by the double-headed arrow 42. After the antennasegments 13 and 14 are adjusted and tightened, the bolt assemblies 37are loosened and the feed strap clamp 34 is moved along the segment 14to thus modify the input impedance of the antenna to compensate forchanges in input impedance caused by the relative movement of thesemi-circular conductors.

r V g 4.

This may be accomplished trial and error to determine the point ofmaximum power transfer. After this point is located, the "boltassemblies 37- aretightened and the antenna is ready for operation.

a It is understood, of course, that the antenna is preferably mounted ina horizontal plane as -viewed in FIGS; 2 and 3 of the drawing. 'Itis'also understood that'the segments 13 and 14,-while shown to containtwo substan! tially parallel conductors connected together at the ends;this antenna'mayinclude a greater number" of circular segments such asfor example 6 or 8 substantially parallel semi-circular tubes connectedat their ends.

It is further understood-that this antenna isi'suitable I by Well knowntechniques'of conductive contact to constitute a circular conductoropened at a gap between said capacitor plates, cooperative for-bothtransmitting and receiving high frequency Waves 1" andlthat variousphysical sizes maybe employed to determine the overallband of frequency"to which the antenna may be'tuned. 4

, While I have shownv and described one illustrative embodiment of thisinvention, it is understood that. the concepts thereof may be applied toother embodiments without-departingfrom the spirit and scope, of this invention. 3

What is claimed is: v

A circular-type antenna comprising'a'pair of identical semi-circularconductors, a-capacitor plate permanently mounted in'afixed 'positionponone end of .each conductor,

a mounting vbracket affixed near the other end of reach conductor, amounting plate for supporting each of said brackets with said"conductors held symmetrically in adjustablemeans in said brackets andsaid mounting plate for moving bothzsaidtconductors apart the sameamount to -vary the distancevb'etweenlsaid capacitor plates whilemaintaining the inductive 'gcomponent of the antenna identical inbothconductors; and a feed line constituting the 'sole conductiveconnection. to said semi-circular conductors coupled rat a position'ofpredeterminedffeed line impedance established on said? conductors;

7 References Cited by the Examiner 2 UNITED STATES "PATENTS 84 6,57 1 fS/SZjGermanyL 867,256 2/53 Germany. 707,573 54 Great: Britain. 7

SAAL ACHQ Primary Examiner.

